1. Field of the Invention
The present invention relates to a sheet feed mechanism, and more particularly to a sheet feed mechanism for reliably feeding sheets or sheet-like image recording mediums, such as photographic films, stimulable phosphor sheets, or the like, one by one from a magazine under a swinging action of suction cups that are coupled to a vacuum source, for holding the fed sheet or sheets so as to be ready for being further fed, and for identifying a sheet with an identifying means which is moved closely to the sheet in ganged relation to removal of the sheet.
2. Prior Art
There is known a stimulable phosphor which, when exposed to radiation such as X-rays, .alpha.-rays, .beta.-rays, .gamma.-rays, cathode rays, or ultraviolet rays, stores a part of the energy of the radiation. When the phosphor exposed to the radiation is subsequently exposed to stimulating rays such as visible light, the phosphor emits light in proportion to the stored energy of the radiation.
Various proposed radiation image recording and reading systems employ sheets of stimulable phosphor. In such a system, the radiation image information of an object such as a human body is recorded in a stimulable phosphor sheet, the stimulable phosphor sheet is then scanned with stimulating rays of light to emit light representing the recorded radiation image information, and then the emitted light is photoelectrically read to produce an image signal which is subsequently processed to reproduce a radiation image as a visible image on a recording medium such as a photographic photosensitive medium, a CRT, or the like.
The radiation image recorded on a stimulable phosphor sheet is read in the radiation image recording and reading system as follows:
The stimulable phosphor sheet is two-dimensionally scanned with a light beam such as a laser beam, and light emitted from the stimulable phosphor sheet in response to the application of the light beam is detected by a light detector such as a photomultiplier tube to produce timeseries image information. The two-dimensional scanning of the stimulable phosphor sheet with the light beam is normally effected by mechanically feeding the stimulable phosphor sheet in one direction for auxiliary scanning thereof while at the same time applying the light beam, which is cyclically deflected in a direction normal to the direction in which the stimulable phosphor sheet is fed, to the stimulable phosphor sheet for main scanning thereof.
The radiation image recording and reading system is basically composed of an image recording unit for recording a radiation image on a stimulable phosphor sheet, a sheet feeder for feeding the stimulable phosphor sheet along a predetermined path, an image reading unit disposed in the path and including a stimulating light source for emitting stimulating light rays to scan the stimulable phosphor sheet and a photoelectric reader for reading light emitted from the stimulable phosphor sheet upon application of the stimulating light rays to produce an image signal, and an erasing unit disposed in the path, for discharging any residual radiation energy from the stimulable phosphor sheet after the radiation image has been read therefrom in the image reading unit and before a new radiation image is recorded on the stimulable phosphor sheet in the image recording unit. The image recording unit, the sheet feeder, the image reading unit, and the erasing unit are assembled in one housing. A stack of stimulable phosphor sheets each bearing image information of objects is accommodated in a magazine, which is loaded in the system. The stimulable phosphor sheets are fed one by one from the magazine into the image reading unit by suction cups.
To each of the stimulable phosphor sheets, there is applied a bar code representative of an identification of the object whose image information is recorded on the stimulable phosphor sheet, image recording conditions, and other information.
Sometimes, a plurality of stimulable phosphor sheets may be fed at the same time by the suction cups, and hence stimulable phosphor sheets may not smoothly be fed one at a time to the image reading unit. In most cases, plural stimulable phosphor sheets are simultaneously fed because they stick electrostatically to each other.
One solution is to use a mechanism for enabling the suction cups to make a swinging action to separate stimulable phosphor sheets from each other when they stick together. Such a mechanism is very complex in structure if it is of a mechanical nature, or requires a complicated process if it is of an electrical nature. Therefore, the mechanism is considerably expensive to construct.
Another problem which arises when stimulable phosphor sheets are given a swinging action by the suction cups is that sticking stimulable phosphor sheets tend to fall from the stimulable phosphor sheet attracted to the suction cups into a position between the magazine and a feed roller or into a shutter slot defined in the magazine, with the result that a next stimulable phosphor sheet cannot smoothly be fed from the magazine. If the above trouble occurs, then it is necessary to take out the magazine, place the stimulable phosphor sheets which have fallen back into the magazine, and load the magazine back into place for further sheet feeding operation.
The system includes a bar-code reader for reading the information from the bar code of each stimulable phosphor sheet, and a feed mechanism for feeding stimulable phosphor sheets one by one from the magazine, the feed mechanism being independent of the bar-code reader. Actually, after the feed mechanism operates to feed a stimulable phosphor sheet from the magazine, the bar-code reader is reciprocally moved in a direction normal to the direction in which the bar code is scanned, thus reading the information from the bar code. Since a stimulable phosphor sheet is fed and its bar code is read in different processes, the cycle time required to complete the operation of the bar-code reader and the feed mechanism is long. Another drive source is needed to move the bar-code reader in reciprocating strokes. The system is therefore relatively large in size and expensive to manufacture.